My advice is to homeschool and follow your ds's lead, taking it one step at a time. Remember, he's 5 and perhaps this is the least-worst or best fit at the moment. It really depends on how fast he accelerates and what happens over the next couple of months/yrs. Nothing is itched in stone and most decisions are reversible.
By all means, you could use a general curriculum elementary series to make sure the basics are covered. And do NOT be afraid to radically accelerate your child either. He may well be able to do math at 4+ grades ahead. Until he's presented with the material, you may not really know what he's capable of doing. Even then, he might hide his true capabilities and potential.
I don't know how PA is with 2e kids or ones who need radical acceleration. However, based on the fact that your ds has blown through a couple of grades of math, I'd say that's really the issue with the schools. Often times, the anxiety and social/emotional issues will subside once these kids have their cognitive needs met. So if he can easily do 5th grade math, for example, it would be a form of torture for him to be with other 5-yr-olds who are barely adding single digits. IF the schools are not willing or unable to accommodate an advanced learner, then you might be banging your head against a wall.
My ds is now 9 and I'm un/homeschooling, but I was in similar shoes to you when my son was 5 and in pre-k. He, too, had been in three different schools within one year. He flew through the math and the schools didn't know what to do with him. I had to learn to follow my gut instinct and frequently disregard or dismiss with many 'experts' said. Yes, I've had the alphabet soup too.
Personally, I think a 1/2 hr of reading and math per day is plenty. Some days, you'll likely have more; some days you'll likely have less. If your ds wants to do more, let him. That's my two cents.
